As described by Shigeyasu Kobayashi, ["Interferon" (1975), published by Kodansha, Ltd., Tokyo], by D. A. J. Tyrrell, ["Interferon and Its Clinical Potential" (1976), published by William Heinemann Medical Books, Ltd., London] and in "Protein, Nucleic Acid and Enzyme", vol. 21, no. 4 (1976), published by Kyoritsu Shuppan Co., Ltd., Tokyo, interferon is a term to define a substance which is a proteinaceous substance induced intracellularly or extracellularly by living cells on exposing the cells to interferon inducers such as virus, bacterium, protozoa, rickettsia, nucleic acid, endotoxin and polysaccharide, and which has an activity to inhibit nonspecifically the multiplication of various viruses in the cells.
Based on this activity, interferon has been regarded as a promising preventive and therapeutic agent for viral diseases since it was discovered.
In recent years, the realization of interferon as a medicinal was in great expectation because it has been recognized as having antitumor activities on nonviral or viral tumor.
Since interferon is species specific, only interferon derived from living human cells is effective in the prevention and therapy of human diseases.
Conventionally, leucocytes were used as living human cells to prepare interferon. Leucocytes are obtained by separation from fresh blood, but their preservation and supply, in a large quantity and at a low cost, are extremely difficult.
Utilization of living cells obtained by inoculating established human cells to nutrient media and cultivating them in vitro was also attempted for the production of interferon. The in vitro methods, however, are impracticable on a large scale and at a low cost, having the disadvantages of requiring a large amount of human serum, and giving unstable multiplication, low multiplication rate and low cell concentration.
Due to the above situation, industrial production of interferon feasible for prevention and/or therapy of human diseases has not so far been realized.